I did migrate from one hardware configuration to another in the past. My systems were initially Dell P4 Celeron machine with an Intel WAN NIC and 2x 3Com LAN LAN NICs. Then I went to an AMD Duron system with an on-board Realtek WAN and the same 3Com LAN NICs. And from there I migrated to an HP Atom micro-ATX PC with an Intel LAN NIC and onboard Realtec WAN.

Every time I backed up and restored the configuration. I did have to re-assign interfaces and that was it.